When driving on sharp bends at high speed and/or during heavy braking, it is perfectly possible for the tires to skid on the ground and this causes the driver to lose control of the vehicle. If the ground surface is wet or frozen, this possibility becomes stronger; therefore, enhancing the traction is a need for approved safety. Developments in tires and road services have sought to optimize the tire-road friction coefficient. On the other hand, there have been some efforts over the years to improve vehicle traction and braking capability by means of increasing the normal loading on the tires without increasing the total vehicle mass.
Several suggestions have been made to employ vacuum-type devices in order to increase normal force in some patents such as U.S. Pat. No. 6,336,515, US2011/0017538A1, U.S. Pat. No. 3,628,625, 3,768,599, 4,044,862, 4,699,252, and 4,896,749. In nearly all of them, a piece having a chamber attached to the vehicle is placed in contact with or close to the road surface and the air contained in the said chamber is evacuated in an emergency. So, the generated vacuum creates a load which is transmitted to the vehicle and increases the traction of the vehicle; or generates an additional braking force during the braking operation.
Unfortunately, these systems suffer from many disadvantages. Many of them are useful only when braking and have no effect on the traction of the vehicle when no braking operation is carried out; and the others have limited ground clearance problems. Some of them transmit high forces into the suspension and many of them require large installations. These disadvantages are to be solved in the present invention.